The present invention relates to a supplemental suspension system for vehicles such as small trucks. More particularly, the invention relates to a method for supplementing the suspension of vehicles such as small trucks.
Conventional small truck chassis have a pair of leaf spring assemblies which connect the axle housing to the frame of the truck. The conventional leaf spring suspension system functions well under the heavy loads for which it was designed, but does not proVide a very comfortable ride when empty.
In order to soften the suspension and provide a smoother ride, it is possible to remove the heavier load bearing springs, but this sacrifices the load bearing capacity of the vehicle.
Heretofore, air suspension systems have been proposed to soften the suspensions of small trucks, but the prior art suspensions are complicated and difficult to install. In many cases, the prior art suspensions can only be added after the existing suspension has been entirely removed. Some prior art suspensions require significant alteration to the truck chassis, which is both expensive and inconvenient. Installation of these prior art suspensions requires readjustment of the tracking of the vehicle and realignment.
A vehicle suspension system incorporating air springs is disclosed in U.S. Pat. No. 4,580,809, to Leaf. The suspension system of the patent would require that the existing leaf springs be cut roughly in half, the axle would rest on the cut-off end of the springs. An air spring would be connected to the leaf springs by a spring seat, and the air spring would be disposed to the rear of the axle and between the spring seat and the frame of the vehicle. The suspension of the patent could only be installed after much labor and significant alteration of the existing leaf spring suspension system. The disclosed suspension also requires a torque arm to hold the axle and frame in lateral alignment.
A method for converting a conventional truck chassis to an air suspension system is disclosed in U.S. Pat. No. 4,580,798. In order to install the suspension of the patent, it is necessary to remove all load-bearing springs and to cut the main leaf spring in half. The remaining half leaf spring is used to support the L-shaped arms of the air suspension system. The air springs are mounted toward the rear of the vehicle between the L-shaped arms and the frame. This prior art suspension also requires the virtual total removal of the existing suspension and significant installation work. Systems similar to the above prior art suspension are disclosed in U.S. Pat. Nos. 3,802,718 and 3,531,099.
An air cushion system for installation on existing suspension systems is disclosed in U.S. Pat. No. 3,499,662, to Paul. In the system according to this patent, an air container is inserted between the vehicle frame and the spring suspension structure to separate the normal bearing surface of the spring suspension from the frame when the vehicle is unloaded, or to Otherwise modify the assoCiation between the frame and spring suspension to substitute the cushioning of the air spring for the stiffness of the normal leaf spring suspension. The system disclosed in the patent is attached to the ends of existing leaf springs, and works by lifting the vehicle either partially or totally from the spring hangers. The prior art suspension works directly through the existing system and therefor does not allow the removal of the heavier load-bearing springs to soften the ride.
Other prior art air suspension systems are disclosed in U.S. Pat. Nos. 3,664,681 and 3,866,894.
It is therefore an object of the present invention to provide a supplemental air suspension system and load leveler for vehicles such as small trucks.
It is an additional object of the present invention to provide a supplemental air suspension system which can be easily installed while maintaining the factory tracking and alignment of the vehicle.
It is yet another object of the present invention to provide a supplemental air suspension system capable of being mounted on both drive axles and other axles.
A further object of the present invention is to allow the removal of the heavier load-bearing springs without sacrificing the load-bearing capacity of the entire suspension.
Another object of the present invention is to provide a method for supplementing a conventional vehicle chassis with an air suspension system in an economical fashion with a minimum of alteration to the vehicle chassis.
A still further object of the present invention is to supplement the existing suspension of a vehicle, while retaining and using the main leaf spring in its entirety, and using only those load bearing springs sufficient to control axle torque during heavy braking or operation of the vehicle.